V8 Networked Multifunction System-Case

2017/11/10

Related products： V8 Networked Multifunction System

EM complements reflection seismic and reduces risk

Oil and gas exploration companies have used the reflection seismic technique for years and rely on its strengths while recognizing its limitations. Factors in the geologic structure of the prospective area can form a high-velocity barrier, degrading resolution below the barrier and limiting the depth of investigation. Volcanic rocks near the surface or in the section, dense, highly-indurated limestone, and crystalline basement thrust over sediments are common obstacles to definitive modelling with seismic. In addition, rugged terrain, jungle vegetation, and geographic remoteness can make seismic difficult, costly, or even impossible to use.

Many oil companies world-wide have used electromagnetic (EM) methods as a cost-effective, useful complement to seismic techniques and as a substitute where seismic cannot be used at all. Both natural-source methods (MT) and man-made, controlled-source methods (IP and CSEM) have made valuable contributions in refining geologic models, reducing exploration risk, and improving production monitoring.

MT provides more detail for structural and statigraphic interpretation

Magnetotellurics (MT) is the most commonly used technique. From the natural signal of the earth's magnetic field, MT derives a resistivity-vs-depth image of the subsurface. At a basic level of interpretation, resistivity is correlated with different rock types. High-velocity layers are typically highly resistive, whereas sediments - porous and permeable - are much less resistive.

While high-velocity layers are an acoustic barrier, their electrical resistivity means the magnetic signal passes through almost unimpeded, allowing MT to see deep beneath these layers.

MT data provides both dimensionality and directionality indicators, adding more detail to structural and stratigraphic interpretation.

Patterns of resistivity are direct hydrocarbon indicators

The presence of hydrocarbons in rocks is also associated with characteristic resistivity patterns revealed by MT - so-called "Direct Hydrocarbon Indicators" - as demonstrated by the international Project Paleorift in Uzbekistan in 2002.